**3. Sugarcane bagasse incineration for energy generation in sugar mills**

Burning or incineration in a boiler for steam generation is the most common application of bagasse using a cogeneration system for steam and power generation [22]. This allows supplying heat and power to the sugar and ethanol process and exporting any excess. In countries such as Brazil, where sugarcane industry is well developed, power generation has been largely supported by the government incentives and can be a major revenue component, after sugar and ethanol sales. **Figure 2** shows the two simplified typical cogeneration systems used.

The backpressure steam turbine (BPST) system in **Figure 2a** is more common. In this system, only the amount of bagasse necessary to match the heat required for the process is burned, thus leaving some excess bagasse that can be used for other purposes or needs to be disposed of. The steam is produced from water treated to remove some minerals and is called boiler feed water. The less efficient old systems generate steam at medium pressure of 22 bar and a temperature of 300°C, while the most modern systems can operate at up to 100 bar and 530°C [22]. The steam is then passed through the BPST with a discharge pressure of 2.5 bar and 140°C to meet the low-pressure steam required by the sugar refinery. The condensing

**Figure 2.** Typical cogeneration systems in sugarcane refineries using (a) a backpressure steam turbine (BPST) and (b) a condensing extraction steam turbine (CEST).

extraction steam turbine (CEST) system in **Figure 2b** is more complex and more expensive than BPST, but achieves higher efficiencies and higher electricity surplus, have more flexibility and can operate the whole year. In this system, the high-pressure steam can be expanded at different lower pressure levels and extract the steam required for process or produce further electricity. Typically, the high-pressure steam is at 65–100 bar and can be expanded at 22 and 2.5 bar with a final condensing stage at 0.135 bar.
